Evolution of a titanic negative North Atlantic oscillation (-NAO) pattern is indicated during the medium-range. The effect of -NAO is to produce anomalous upper-level high-pressure blocking over Greenland. The high-pressure block is certainly evident in the “most likely” upper air forecast for the northern hemisphere by the mega-cluster ensemble.

In a worse case scenario, the evolving cold pattern in Western Russia is trending stronger and is now more expansive into Europe likely reaching U.K. in the medium range. The Canadian Ensemble most effectively illustrates the cold risk.